1. Field of the Invention
The present invention relates to a positive photosensitive composition for use in the process of producing a semiconductor such as IC, in the production of a circuit board for liquid crystal, thermal head and the like, or in other photofabrication processes, and a pattern forming method using the same. More specifically, the present invention relates to a positive photosensitive composition suitable for the processing where an exposure light source of emitting a far ultraviolet ray or the like of 250 nm or less, preferably 220 nm or less, or an irradiation source utilizing an electron beam or the like is used, and a pattern forming method using the same.
2. Description of the Related Art
The chemical amplification-type photosensitive composition is a pattern forming material capable of forming a pattern on a substrate by producing an acid in the exposed area upon irradiation with actinic rays or radiation and through a reaction using this acid as the catalyst, changing the solubility in a developer between the area irradiated with actinic rays or radiation and the non-irradiated area.
In the case of using a KrF excimer laser as the exposure light source, a resin having small absorption in the region of 248 nm and having a basic skeleton of poly(hydroxystyrene) is predominantly used as the main component, and this is an excellent system capable of forming a good pattern with high sensitivity and high resolution as compared with the conventional naphthoquinonediazide/novolak resin system.
In the case of using a light source of emitting light at a shorter wavelength, for example, in using an ArF excimer laser (193 nm) as the light source, a satisfactory pattern cannot be formed even by the above-described chemical amplification system because the compound having an aromatic group substantially has large absorption in the region of 193 nm.
In order to solve this problem, a resist containing a resin having an alicyclic hydrocarbon structure has been developed as the resist for use with an ArF excimer laser.
Furthermore, it has been found that the performance is enhanced by containing a repeating unit having a lactone structure in the resin having an alicyclic hydrocarbon structure. For example, JP-A-9-73173 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”)), U.S. Pat. No. 6,388,101B, JP-A-2000-159758, JP-A-2001-109154 and U.S. Patent Publication 2001-26901A describe a resist composition containing an acid-decomposable resin having a lactone structure.
Also, U.S. Pat. No. 6,627,391B describes a composition containing an acid-decomposable resin and a low molecular additive having a lactone group.
However, it is actually very difficult to find out an appropriate combination of a resin, an acid generator, additives, a solvent and the like from the aspect of overall performance as the resist. Furthermore, in forming a fine pattern having a line width of 100 nm or less, the formed line pattern falls despite excellent resolution performance and improvements are demanded not only in the problem of pattern falling giving rise to a defect at the production of a device but also in the line edge roughness performance of a line pattern.
Here, the line edge roughness means that the edge of the interface between the resist line pattern and the substrate irregularly fluctuates in the direction perpendicular to the line direction due to characteristics of the resist and when the pattern is observed from right above, the edge gives an uneven appearance (evenness of approximately from ±several nm to several tens of nm). Since this unevenness is transferred onto the substrate by an etching step, if the unevenness is large, an electric characteristic failure and in turn reduction in the yield are caused.